In order to determine the clinical in-hospital course of patients with acute myocardial infarction treated with intravenous Streptokinase (SK), 132 patients were studied divided as follows: Group I: 44 patients who arrived to the hospital within 6 hours from the onset of symptoms and received fibrinolytic therapy. Group II: 44 patients who arrived more than 6 hours delay and did not receive SK. Group III: 44 patients who arrived less than 6 hours delay but they did not receive SK. The overall hospital mortality was 2.2% in the SK recipients versus 4.4% in the group II (Odd ratio 0.95, p = NS) and 13.6% in group III (Odd ratio 0.79, p greater than 0.05). The incidence of hemorrhagic episodes was not increased in SK recipients. In-hospital period differences between groups were explained by protocol studies and postoperative complications in patients that needed further revascularization procedures.